Shimano crank set compatability

[Radlerin]

I need to replace the triple crank set on a bike. The name of the bike (a road bike, or possibly a hybrid) is "Bulls" (presumably a German brand), new in 1999. The Shimano crank set has FC-MC 18 stamped on it. I'm not sure how easy it is to replace something this old. That is my first question:
1) Does anyone know where I could source an identical replacement?
I'm not averse to replacing it with a different, more recent Shimano crank set, if that is my only option, which leads to the next question:
2) How on earth am I to establish which other Shimano crank sets, if any, are compatible with the spindle on my bike?
The spindle appears to be rather short. My awkward attempts to measure it arrive at a value of approximately 110mm. The spindle actually protruding from the cassette is only about 18mm - 20mm on each side.....way shorter than the visible spindle length on the MTB.
There is a plethora of triple crank sets on offer on ebay, but invariably in the description the level of detail offered falls short of what I require to eliminate the possibility of buying sight unseen something that bottoms out on my puny little spindle. So, question 3:
3) Does anyone know if I can use another brand crank set, i.e. one that will fit on a protruding spindle length of roughly 20mm?
I'm guessing my spindle is J.I.S. taper.....but am not sure if it is standard or low profile.
I appreciate any light anyone can shed on this topic.

[Nobody]

Just get whatever cranks you want, matching the crank arm length and the number and size of chainrings you require. Then get the bottom bracket the manufacturer recommends, usually with a recommended spindle length. Most likely your bottom bracket shell will be the standard English BSA. Remember that the bottom bracket shell has a left hand thread on the right side of the bike (for BSA).

[find_bruce]

I feel your confusion & will try to keep things simple so I can understand it.

But first a question, why do you think you need to replace the crank - worn out chainrings, bottom bracket or have you somehow broken a crank arm or spider ? If all you have done is wear out a chainring, they are pretty simple to replace.

What you have
the FC-MC18 is an Alivio spec crank. Shimano's highly developed niche manufacturing is confusing, perhaps deliberately so, but Alivio is towards the bottom in terms of the quality. It is not a bad spec, & has bolted chainrings, not riveted, but perhaps a little heavy. That puts it above Acera, Altus, Tourney & generic components. It came with 22-32-42 teeth chainrings.

As always, the late, great Sheldon is your friend. A couple of things you should read which helped me to understand - Bottom Bracket Sizes Bottom Bracket Spindle Tapers and Chainline

In your case, the cranks will use JIS square taper, with a British/ISO bottom bracket (1.375" X 24 tpi, standard thread on left, left hand thread on the drive side), most likely a chainline of 47.5mm, which is consistent with the measurement of 110 mm for the axle. According to Sheldon the JIS low profile was only used on some Dura Ace so you shouldn't have to worry about that. The good news is that almost any shimano square taper triple crank (ie not dura ace) will fit your spindle taper & length.

Sourcing a direct replacement
You are most unlikely to find an identical replacement for your cranks - they were only made for a couple of years & that was a while ago.

2 - Easy Option
If the bottom bracket is good, buy almost any shimano square taper triple crank (ie not dura ace), pick the number of teeth for the chainring - if you are happy with the current set up, look for 22-32-42. eg Alivio M410 or Acera M361.

2- Slightly harder option
To get more readily available cranks, all you will have to do is change the bottom bracket. Eg I recently purchased Deore M590 cranks. Because this needs an external bottom bracket, you will need to get a LBS (Local Bike Shop) to face your bottom bracket. This is going to add about $50

Other manufacturers
Pretty much any other square taper crank will work - see the Sheldon article on Bottom Bracket Spindle Tapers. The problem is that it is even harder to find a square taper crank from other manufacturers

[Duck!]

I feel your confusion & will try to keep things simple so I can understand it.

But first a question, why do you think you need to replace the crank - worn out chainrings, bottom bracket or have you somehow broken a crank arm or spider ? If all you have done is wear out a chainring, they are pretty simple to replace.

What you have
the FC-MC18 is an Alivio spec crank. Shimano's highly developed niche manufacturing is confusing, perhaps deliberately so, but Alivio is towards the bottom in terms of the quality. It is not a bad spec, & has bolted chainrings, not riveted, but perhaps a little heavy. That puts it above Acera, Altus, Tourney & generic components. It came with 22-32-42 teeth chainrings.

Alivio is one step below Deore. That places it as roughly equivalent to Sora in road hierarchy. Given the wider range of MTB component levels, that ranks it as lower mid-range.

2 - Easy Option
If the bottom bracket is good, buy almost any shimano square taper triple crank (ie not dura ace), pick the number of teeth for the chainring - if you are happy with the current set up, look for 22-32-42. eg Alivio M410 or Acera M361.

Shimano have a somewhat annoying habit of altering the offset of the chainrings from the crank butt. Older cranks tended to have the inner face of the crank butt on the same plane as the small chainring, but newer cranks tend to have the chainrings offset inward. The result is that a new crank on the old BB will likely foul the chainrings on the frame, so a new BB would be required.

2- Slightly harder option
To get more readily available cranks, all you will have to do is change the bottom bracket. Eg I recently purchased Deore M590 cranks. Because this needs an external bottom bracket, you will need to get a LBS (Local Bike Shop) to face your bottom bracket.

That is generally not needed, and in fact not recommended by frame and component manufacturers, as it affects the tolerance for the overall assembled width of the bottom bracket, which is somewhat critical with modern two-piece crank arrangements

Other manufacturers
Pretty much any other square taper crank will work - see the Sheldon article on Bottom Bracket Spindle Tapers. The problem is that it is even harder to find a square taper crank from other manufacturers

No it's not.

[Radlerin]

Thank you all for your advice. It seems an unnecessary expense to replace the BB, as it is fine. The reason I would like to replace the entire crank set rather than just the chain rings is that all three are worn. find_bruce, thanks for providing the links to the two cranks. I had a look at them (Alivio FC M410 and Acera M361). The Alivio listing neglects to mention the spindle length at all, and the Acera gives a spindle length of 122.5mm, and says it is a MTB triple. As my entire spindle length is a good 10mm shorter, and the MTB crank set I have tried to put on it won't fit, won't I find that the Acera is for a bike with much longer visibly protruding spindles?
I would be happy with any brand crank set that fits, by the way. Quality is no longer an issue. When I first got the bike I used it incessantly for commuting, and hammered it fully loaded on trans-Europe treks.....now I'm refurbishing it for my boyfriend to use to noodle down the road to check the surf. He certainly won't be doing the Giro d'Italia on it, so if there is something non-Shimano with a correspondingly non-Shimano price, but with the right dimensions to fit my little spindle, I'm content.

[find_bruce]

Raderlin, I make no pretence of expertise & you are wise to check what I say - I can & do make mistakes. I usually look up the component on http://techdocs.shimano.com/techdocs/index.jsp" onclick="window.open(this.href);return false; to see what is needed. In this case the service instructions for the M410 say it needs a 113mm spindle, but that is for a 50mm chainline. If I understand it correctly, your 110mm spindle will maintain your 47.5mm chainline.

Duck, do you have a link to these readily available square taper cranks to suit a 110mm spindle with a 47.5mm chainline ?

[Radlerin]

find_bruce, I clicked on the service instructions for fc m410 on the Shimano page. The second table (bottom bracket) seems to show that the fc m410 corresponds to LL113.....does that mean that it is suitable for a 113mm long spindle?

[find_bruce]

That's the way I am reading it- a 113mm spindle to give you a chainline of 50mm.

Sheldon's bottom bracket size page shows the Alivio MC18 as using a spindle of 110mm to give a chainline of 47.5mm or 113mm to give a chainline of 50mm.

Ie it looks to me to be a direct replacement for your current crank.

[Radlerin]

It looks like the fc m410 is the way to go. Thanks so much for your help.